﻿//
// Copyright 2023 Google LLC
//
// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
// 
//   http://www.apache.org/licenses/LICENSE-2.0
// 
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.
//

using System;
using System.Diagnostics;
using System.Reflection;

namespace Google.Solutions.Common.Util
{
    public static class Invariant
    {
        /// <summary>
        /// Verify that a variable is not null.
        /// </summary>
        public static T ExpectNotNull<T>(
            T? value,
            string variableName)
            where T : class
        {
            Debug.Assert(
                Assembly.GetEntryAssembly() == null || // Running a test case
                value != null);

            if (value == null)
            {
                throw new ArgumentNullException(
                    $"The variable {variableName} must not be null");
            }

            return value;
        }
    }
}
